Here's how quickly a car heats up in the sun — and why you should never leave anyone there
- A car can heat up very quickly in the sun, or even in the shade.
- In fact, temperatures can reach dangerous levels within an hour, which can lead to heatstroke and even be fatal.
- Don't leave anyone in the car when it's hot out — especially children, older people, or animals — as they are at a higher risk for heat illness.
- This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine.
When it's hot outside, cars are a dangerous place to be — especially for children, the elderly, and pets. That's because a car's internal temperature can rise very quickly, even in the shade.
On average, 39 US children under the age of 15 die every year from heatstroke because they were left in a hot car. In fact, it's illegal in 20 states — including California, Texas, Florida, and Illinois — to leave a child unattended in a vehicle.
Here's how quickly temperatures rise in a car, and why it's important to take these warnings seriously.
How hot does a car get in the sun?
On a hot day, the temperature inside a car can rise to dangerous levels in less than an hour. This chart can help you understand just how hot a car gets in the sun, depending on the outside air temperature:
For example, a 2018 study published in the journal Temperature took three vehicles of identical models and placed them in either direct sun or under shade in Tempe, AZ. When parked in the sun, a car's internal temperature increased from 85°F to 116°F in just an hour, while it reached 101°F in the shade.
"Light comes into the car through the windows, but heat can't get out, and so the car gets much hotter than outside," says Jaiva Larsen, MD, a physician in the Emergency Medicine Department of the University of Arizona Health Sciences. "In a parked car, the temperature can go up 20 degrees Fahrenheit in just 10 minutes."
A 2005 study published in Pediatrics found that even rolling down the windows might not make a difference. When the car windows were closed, the temperature rose 3.4°F per minute, and when the windows were rolled down about 8 inches, the temperature still rose 3.1°F per minute.
"Many parents are surprised to learn that cracking the window open does little to keep the car cool," says Skyler Kalady, MD, a pediatrician at Cleveland Clinic Children's Hospital.
Don't leave anyone in the car
Even if you don't think it's that hot out, leaving somebody in a car — especially a child — can be dangerous. Extreme heat may cause heat exhaustion, which can then develop into heatstroke and lead to organ damage or death, if left untreated.
Here's why you should never leave your children, pets, or elderly relatives in a car, no matter the circumstances.
Children
Due to their smaller size, a child's body heats up three to five times faster than an adult's.
Children also haven't fully developed the ability to cool themselves down, so they can't lower their body temperature as efficiently when sweating.
When left in a hot car, a child will first start overheating. Symptoms of overheating in children include:
- Dizziness
- Disorientation
- Rapid breathing
- Nausea
- Vomiting
- Unconsciousness
A car reaching 104°F can cause heatstroke in a child, and 107°F can be deadly. More than half of children who die in cars because of extreme heat are under two years old.
Senior citizens
The elderly are also at risk of heat-related injuries. According to a 2018 study, people 60 or over are more likely than any other age group to be harmed from extreme heat.
Like children, elderly individuals also can't regulate their body temperature as well as younger adults. In addition, there are certain risk factors for older people that can increase heat-related injuries:
- Living alone. Whereas children usually have a parent watching over them, elderly people might not get the help they need if they have heat exhaustion or heatstroke symptoms.
- Medications. Some medications can hamper an individual's ability to regulate their temperature, such as drugs that can help control high blood pressure, which is a more common condition among older people.
Animals
Pets are also susceptible to heat when left in cars. A dog's normal body temperature is about 100.5°F to 102.5°F, but in a hot car, their bodies can reach between 106°F and 109°F — hot enough to cause damage to their organs and circulatory system.
According to the American Society for the Prevention of Cruelty to Animals, signs of overheating in a dog include:
- Drooling
- Excessive panting
- Difficulty breathing
- Weakness
- Stupor
- Seizures
- Collapse
The bottom line
You should not leave pets, children, or elderly adults unattended in a vehicle on a hot day — not even for a minute.
Even the air conditioning isn't sufficient to protect a child, pet, or elderly person. When unsupervised, all three can accidentally put the car in gear or shut the air conditioning off.
Overall, the New York State Department of Health advises taking your child with you for all errands or using drive-thrus as much as possible.
"Don't overthink it," Larsen says. "Don't try to calculate how hot it's going to get in a car under particular conditions. Just don't leave kids or pets in a car."